Mechanisms Of Actions

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Antimycobacterium drug: Isoniazid

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used in treatment of tuberculosis, interferes with cell wall synthesis in mycobacterium by inhibiting the production of mycolic acid, an analog of pyridoxine (Vitamin B6) & it may inhibit pyridoxine catalyzed reactions, activated by a mycobacterial peroxidase enzyme

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Antimycobacterium drug:
Ethambutol hydrochloride

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interferes with cell wall synthesis, it inhibits incorporation of mycolic acids into the mycobacterial cell wall

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Fluoroquinolones (ciprofloxacin

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): interact with DNA gyrase

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Nalidixic acid: quinolones:

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interferes with DNA replication, effects DNA gyrase, it binds to the cleavage complex composed of DNA and gyrase during this strand passage, this interaction of it acts to stabilize the cleavage intermediate, leaving the DNA permanently bond to DNA gyrase

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Penicillins

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: interfere specifically with new bacterial cell wall synthesis during cell division the transpeptidation step of peptidoglycan synthesis is inhibited (can’t make cross linkages required for the cell wall)

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Cephalosporins:

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interfere with peptidoglycan synthesis of the bacterial cell wall by inhibiting the final transpeptidation needed for cross-linking

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Aminoglycosides

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inhibit protein synthesis by attaching irreversibly to the 30S subunit of bacterial ribosomes, this attachment interferes with the reading of mRNA molecules, preventing the initiation of protein synthesis (changes shape of 30S)

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Chloramphenicol

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binds to the 50S ribosomal subunit, & inhibits the bacterial enzyme peptidyl transferase (makes peptide bonds) thereby preventing the growth of the polypeptide chain during protein synthesis.

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tetracyclines

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inhibit protein synthesis of growing bacteria by binding to the 30S subunit of prokaryotic ribosomes & preventing the binding of charged tRNA’s

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the macrolide antibiotics

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inhibit protein synthesis by binding to the 23S rRNA molecule (in the 50S subunit) of the bacterial ribosome, this blocks peptide bond formation & translocation

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vancomycin (Vancocin):

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inhibition of cell wall synthesis - inhibits the synthesis of peptidoglycan, specifically inhibits the action of transglycosidase & transpeptidase

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synercid

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inhibits the early phase of protein synthesis, while quinupristin inhibits a later phase of protein synthesis, both bind irreversibly to the 50 S subunit, binding of "d" alters the conformation of the ribosome such that it’s affinity for "q" binding increases, modifying the 70S ribosome results in constriction of the exit channel for the growing protein (blocks translocation) , the protein is stuck at the peptidyl transferase & no more peptide bonds are made

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rifamycin

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: inhibits the synthesis of mRNA by inhibiting the procaryotic RNA polymerase, binds to the beta-subunit of RNAP & blocks the entry of the first nucleotide, thus blocking mRNA synthesis, it blocks the initiation of transcription

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bacitracin & polymyxin B: polymyxin

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interacts with phospholipids in the cytoplasmic membrane, disrupting it & causing leakage of the cellular contents

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Sulfonamides

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this molecule is able to substitute for PABA, during the synthesis of folic acid it binds tightly to the enzyme pteridine synthetase, inhibiting the enzyme, making it unavailable for folic acid synthesis

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Zyvox (linezolid)

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binds to the 23S ribosomal RNA of the 50S subunit, blocks the formation of the 70S ribosomal initiation complex (selectively toxic) inhibits the N-formalin – can never initiate DNA synthesis

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erythromycin

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inhibit protein synthesis by binding to the 23S rRNA molecule( in the 50S subunit) of the bacterial ribosome, this blocks peptide bond formation and translocation